Down-Hole Injection of Butane to Control Paraffin Deposition in Pumping Wells

Results of field tests indicate that butane can be injected easily and economically down the tubing-casing annulus of pumping wells. The quantity and frequency of butane injection varies with each well and, if injected properly, will effectively control paraffin deposition in the tubing and flow lines. Butane has the effect of increasing the solution capacity of the crude oil for the waxy substances being deposited. In the 12 wells tested, a reduction in the cost of paraffin control by as much as 90 per cent was obtained, and in one well the annual reduction totaled $1,000. The expense necessary to install the surface equipment is $165.00 per well, and the injection process is performed by a pumper as a routine duty. The injection of butane to control paraffin deposition at the present time is limited to wells that pump off or pump and flow off and to paraffin or mixed base crudes. Further study may indicate that the process can be utilized in other types of wells. Introduction Paraffin accumulation in tubular goods is a costly problem that has long been associated with crude oil production. One method for the control of this accumulation in pumping wells is the down-hole injection of a butane-crude oil mixture. The purpose of this paper is to outline the process and to indicate the saving that may be obtained in using this method for a more economical recovery of crude oil. Solubility of Paraffin in Hydrocarbon Systems Crude oil, as it originally exists in a reservoir, contains varying percentages of waxes, gums, resins and asphaltic materials which remain in solution until the solution equilibrium has been sufficiently disturbed; then these substances separate from the crude oil and form what is generally known as paraffin deposits. There are a number of factors involved in the separation and deposition of paraffin in crude oil wells; however, temperature decrease and loss of lighter fractions are the most important causes of solubility change and the resultant paraffin separation.